Microfluidic technology has been studied extensively to develop low-cost lab-on-a-chip devices. These devices often require the use of simple, reliable valves to facilitate their operations. Many MEMS-based valving principles, such as utilizing magnetostatics, electrostatics, pneumatics or thermal actuation of movable membranes, have been thoroughly studied, but the fabrication and/or the operation of these valves could still be complicated. Therefore, valves with simple structure such as those operated by using phase-change materials or rheological materials are of great interest.
Unfortunately, there is still a lack of simple microvalves especially for on-chip blood analysis. Interestingly, blood is a fluid that can coagulate under the right conditions, and this coagulation process may provide a natural valving mechanism that has not been well explored in microfluidics. In blood vessels, solid blood coagulum can be formed through biological clotting process to stop bleeding. Similarly, others methods can be used to trigger the blood coagulation. For example, thermal coagulation uses heating to introduce the blood clogging, which is mainly a process of protein denaturation and cross linking. This coagulation property of blood provides an interesting alternative to traditional valving mechanisms. A valve using blood coagulation as the actuation method needs no extra material other than the blood sample itself, which is readily available in devices targeting for blood analysis. Surprisingly, the present invention meets this and other needs.